By sticking its connector in your machine's USB slot, and starting it up holding Command and some other key maybe?
If it comes on a 4GB USB drive I would venture a guess that it apparently fits on one. Does it come on a 4GB USB drive?

Absolutely! In fact, if you're not a developer you don't want an unfinished OS on your machine. Unless you're a masochist of course.
I'm gonna get Lion too, but not before OSX.7.2*. If others want to enjoy bugs, corrupt bits, and endless restarts that's that's their business, but I – as a simple (albeit heavy) user – want a smoothly running OS without headaches and other nuisances.

*I waited until OSX.2.2 before I installed Jaguar, until OSX3.2 before I installed Panther, until OSX.4.2 before I installed Tiger, until OSX.5.2 before I installed Leopard, and I waited until OSX.6.2 before I installed Snow Leopard. Never had OS problems in the entire past decade, because I never installed before 99,9% of bugs had been fixed.